const myHeading = document.querySelector("h1");
myHeading.textContent = "Hello world!";

const myImage = document.querySelector("img");

myImage.onclick = () => {
  const mySrc = myImage.getAttribute("src");
  if (mySrc === "images/firefox-icon.png") {
    myImage.setAttribute("src", "images/7f6fa5336d945a6bd2520fef07282dc7.jpeg");
  } else {
    myImage.setAttribute("src", "images/firefox-icon.png");
  }
};
document.querySelector("html").addEventListener("click", function () {
  alert("别戳我，我怕疼！");
});